Add TruffleRuby in CI (#1079)

* Add TruffleRuby in CI

* Remove continue-on-error in unstable.yml workflow

* This is a daily job, the failures only appear in the Actions tab so
  there seems to be little value to hide it.

* Add comment about running only rake spec on truffleruby

Author: eregon

.github/workflows/stable.yml

@@ -19,6 +19,7 @@ jobs:
           - '3.2'
           - '3.3'
           - jruby-9.4
+          - truffleruby
 
     steps:
       - uses: actions/checkout@v4
@@ -28,5 +29,13 @@ jobs:
           ruby-version: ${{ matrix.ruby-version }}
           bundler-cache: true
 
-      - run: |
-          bundle exec rake
+      - name: Run tests
+        run: bundle exec rake
+        if: matrix.ruby-version != 'truffleruby'
+
+      # Run only `rake spec` on truffleruby, because just `rake` runs `rubocop spec cucumber`.
+      # There is no value to rerun rubocop here.
+      # cucumber fails because it uses an old childprocess which depends on fork.
+      - name: Run specs (truffleruby)
+        run: bundle exec rake spec
+        if: matrix.ruby-version == 'truffleruby'

.github/workflows/unstable.yml

@@ -17,6 +17,7 @@ jobs:
         ruby-version:
           - ruby-head
           - jruby-head
+          - truffleruby-head
 
     steps:
       - uses: actions/checkout@v4
@@ -25,8 +26,14 @@ jobs:
         with:
           ruby-version: ${{ matrix.ruby-version }}
           bundler-cache: true
-        continue-on-error: ${{ (matrix.ruby-version == 'ruby-head') || (matrix.ruby-version == 'jruby-head') }}
 
-      - run: |
-          bundle exec rake
-        continue-on-error: ${{ (matrix.ruby-version == 'ruby-head') || (matrix.ruby-version == 'jruby-head') }}
+      - name: Run tests
+        run: bundle exec rake
+        if: matrix.ruby-version != 'truffleruby-head'
+
+      # Run only `rake spec` on truffleruby, because just `rake` runs `rubocop spec cucumber`.
+      # There is no value to rerun rubocop here.
+      # cucumber fails because it uses an old childprocess which depends on fork.
+      - name: Run specs (truffleruby)
+        run: bundle exec rake spec
+        if: matrix.ruby-version == 'truffleruby-head'

spec/return_codes_spec.rb

@@ -34,6 +34,8 @@
         end
 
         it "prints a message to STDERR" do
+          # https://github.com/oracle/truffleruby/issues/3535
+          skip "fails on truffleruby" if RUBY_ENGINE == "truffleruby" && command.include?("testunit_bad.rb")
           expect(@stderr).to match(/stopped.+SimpleCov.+previous.+error/i)
         end
       end